1. Field of the Invention
The present invention relates generally to an arrangement of encoding motion image signals, and more specifically to such an arrangement wherein a motion region is extracted from an incoming image signal and is used to predict motion compensation and wherein a region to be orthogonally transformed is extracted and undergoes orthogonal transformation.
2. Description of the Prior Art
Digital image encoding has found effective applications ranging from medial imagery, remote sensing up to image communication such as video conference and picture telephone.
Many approaches to effectively encoding motion image signals consecutively applied have been proposed, one of which is discussed in a paper entitled "Coding of arbitrarily shaped image segments based on a generalized orthogonal transform" by Michael GILGE, et al, Signal Processing: Image Communication 1 (1989), pages 154-180, issued by Elsevier Science publishers B.V.
According to this prior art, arbitrarily shaped regions, each of which exhibits a large motion compensated prediction error, are extracted and then subject to orthogonal transformation depending on the shapes theroef.
In more specific terms, each of frame images applied to an encoder is divided into a plurality of grids irrespectively of the content of the image. Following this, motion vectors are derived using so called "block, matching" techniques. The motion vectors are used to motion compensate a preceding frame image and thus, a current frame image is predicted. Throughout the instant disclosure, a "current frame image" implies an incoming frame image.
Subsequently, the regions each of which exhibits a large amount of motion compensated prediction error, are extracted from the current image signal after comparing the predicted image with the current frame image. Thereafter, the region is subject to orthogonal transformation depending on the shape thereof using a base function. After the contour of the region is determined, encoded are the motion vectors and the contours and the conversion coefficients of the orthogonal transformation.
However, the above mentioned prior art encodes the contours using chain codes and hence this prior art has encountered the problem in that a very large amount of information should be transmitted.